It is conventional to use a leaf spring at each side of a vehicle to provide the suspension mechanism between the frame of the vehicle and the axle, such that one end of each spring is pivotally fixed to the frame and the other end connected via a shackle to the frame. In many instances, such as in pickup trucks as well as large trucks, the suspension system is designed to give acceptable rides where the vehicle is substantially loaded, but provide a poor and uncomfortably stiff ride when the vehicle is very lightly loaded as with only the driver and no cargo. In some instances, this condition exists because the rear springs are designed for rated (full cargo) loads and such springs are far too stiff. In addition to the above, helper springs are also used in conjunction with the lead spring but this generally only aggravates the stiff ride problem.
The above mentioned shackle which connects the leaf spring to the vehicle frame are categorized in two ways, as compression shackles or tension shackles. Commonly owned U.S. Pat. No. 5,007,660 (the disclosure of which being hereby fully incorporated herein by reference) describes a torsion spring member being utilized to replace a tension type shackle. Many vehicles, however, are equipped with compression type shackles and therefore the system described in Orndorff, Jr. et al. is inappropriate. What is needed then is a replacement system for compression shackle leaf spring systems. Efforts to improve such systems have lead to continuing developments to improve versatility, practicality and efficiency.